Switch structure with differential adjustment



May 12, 1936. M. PERSONS 2,040,404

SWITCH STRUCTURE WITH DIFFERENTIAL ADJUSTMENT Filed Sept. 15, 1934 Q Mama Patented Ma 12, 1936 UNITED STATES SWITCH STRUCTURE WITH DIFFER- ENTIAL ADJUSTMENT Lawrence M. Persons, Des Moines, Iowa, assignor to Penn Electric Switch 00., Des Moines, Iowa,

a corporation of Iowa Application September 15, 1934, Serial No. 744,156

16 Claims.

The object of my invention is to provide a switch structure with differential adjustment which is simple, durable and comparatively inexpensive to manufacture.

A further object is to provide a switch structure in which the differential is adjusted by stopping an armature in a stronger or weaker magnetic field as required, the adjusting device being associated with a contact carrier element having a leaf spring on which the contact is mounted, the

leaf spring normally constraining the contact to engage the contact carrier element.

- Still a further object is to provide a thermostatic switch having a bimetal element folded in a zigzag formation for condensing the size of the bimetal element yet obtaining considerable ,movement thereof under temperature changes.

Another object is to provide in a switch structure, a contact arrangement whereby in the event of the contacts sticking together, they will be pulled apart by a peeling action when the contactsare separated.

Still a further object is to provide an anticipating type of thermostat in which all the current carrying elements arelocated below the bimetallic or other temperature responsive element which operates the switch so that heat generated in these parts is utilized to hasten the opening of the switch after it has once been closed.

Still another object is to provide a room thermostat or the like with a magnet which widens its differential of operation andpto provide in combination therewith a means to compensate for such widening of the differential by tending to narrow it, such means being in the form of a heating element to cause quicker action of the switch when in closed circuit position than is otherwise possible without such a heater. With these and other objects in view my invention consists in the construction, arrangement and combination of the various parts of my device, whereby the objects contemplated are attained, as hereinafter more fully set forth, pointed out in my claims, and illustrated in the accompanying drawing, in which:

Figure 1 is a front elevation of a switch structure embodying my invention with a cover therefor removed.

Figure 2 is a sectional view on the line 2-2 of Figure 1 showing the cover in position.

Figure 3 is a sectional view on the line 3-3 of Figure 1 showing the association of contacts and a differential adjusting means.

Figure 4 is a view of the lower portion of Figure 1 showing the parts adjusted to a different position; and

Figure 5 is a diagrammatic view of steps in the operation of the switch.

On the accompanying drawing I have used the reference numeral 10 to indicate generally a switch casing, the cover therefor being indicated at l2. The parts l8 and I2 are preferably formed of insulation and the switch structure shown is a type suitable as a room thermostat, especially for baseboard mounting, such as disclosed in my copending application Serial No. 737,057, filed July 26, 1934.

Within the switch casing 10,1 provide a bracket l4 having a flange l6 against which a permanent magnet I8 is mounted as by a plate 20 and a screw 22. A relatively stationary contact 24 is carried by the bracket l4, it being mounted on a leaf spring 26. The leaf spring 26 and a carrier element 28 are secured as by rivets 30 to a flange 32 of the bracket [4. The carrier element 28 is channel-shaped in cross section as shown in Figure 3 to resist bending with the exception of the portion thereof which is secured to the flange 32. This portion and the leaf spring 26 are originally formed of such shape that when riveted in position by the rivets 30, the free end of the carrier element 28 tends to engage the bracket l4, while the contact 24 carried by the leaf spring 26 is constrained to engage the carrier element 28.

A differential adjusting means is provided in the form of a set screw 34 threaded in the bracket -14 (see-Figure 3) and extending into an adjusting sleeve 36. The adjusting sleeve is secured in the proper position at the factory to the adjusting screw 34 by a set screw 38.

The adjusting sleeve 36 is provided with a slot 40 in which a screw driver can be inserted for rotating the adjusting sleeve. The sleeve is provided with a pointer 42 and stops 44 for limiting its movement. The adjusting sleeve is knurled as at 46 and a leaf spring 48 engages the knurling to prevent undesired rotation.

A bracket 50 is provided with which a leaf spring made of prongs or the like 52 1s secured. A bimetal element 54 is secured to the leaf spring as by rivets 56, while on the free end of the bimetal element, an armature or switch arm 58 is secured. The armature 58 is provided with a contact 60 to coact at times with the contact 24 and is provided with an armature piece 62 affected by the magnetic field of the magnet IS.

A range adjustment means is provided in the form of a coarsely threaded set screw 84 threadedly associated with the switch casing II and engaging the leaf spring 52 through an insulating insert 66 to avoid transmission of electricity from. the spring to the screw St. A handle 68 is provided for the screw 64 and may be secured in the proper position thereon by a set screw it.

The bracket 50 has a terminal (2 and connected with this terminal and another terminal It is heater IS. The circuit is so connected that when. the switch is in closed position the current passes through this heater so as to more quickly raise the temperature within theswitch casing Ill than would be possible by the surrounding or ambient temperature alone as caused by the operation oi" a burner controlled by the switch. The magnet l8 widens the differential of the switch, whereas the differential would be slight if the magnet were not provided. However, the magnet is desirable [to cause snap action of the switch and to provide a means for varying the differential as already described.

The heater l6 acts as a means to compensate for this widened differential caused by the magnet because the heater tends to narrow the differential in the following manner.

When the switch closes and current flows through it, it also flows through the heater 16,

.thus raising the temperature within the switch casing l0 and thereby opening the switch sooner than it otherwise would as a result of rise in ambient temperature only.

Another feature of my present switch which tends to narrow the diiferential is that the current carrying parts are located below the bimetal element 5 so that any heat generated therein, when current is passing therethrough, rises and aflects the bimetal in addition to the heat radiated from the heater '16.

Practical operation In the operation 01 the switch structure disclosed, a sumcient increase in room temperature swings the switch arm 58 from its full line position to its dotted line position in Figure 1 for separating the contacts 24 and 60 and a sumcient drop in temperature causes them to engage. The magnet l8 causes snap action, which action is increased or decreased by the differential adjuster 36. when the action is increased as in Figure 4, the difierential is widened and when decreased as in Figure 1, it is narrowed.

The particular construction whereby the spring It carries the contact 24 and normally retains it under the same tension in engagement with the carrier element 28 makes it possible to change the diflerential of the switch without in any way altering the tension of the spring 26 for constraining the contact 24 to remain in engagement with the element 28, whereas with separate mountings, an additional adjustment would have to be provided tor the tension of the spring.

The particular spring mounting for the contact 24 also provides a switch in which sticking of the contacts is overcome whenever it occurs as illustrated in Figure 5. This figure is divided into four sections, namely A, B, C and D.

In section A, the contacts are engaged. In section B, they are being separated but are stuck together. Normally they separate with the spring 26 remaining in contact with the carrier element 28 as in section A, but when they become stuck, the contact 24 will be carried away from the element 28 by the contact 60 as at B. The spring 26 tending to separate the contacts in the position B does not have a direct pulling away action on the contact 24 but rather a twisting action as is readily apparent. This twisting action tends to peel" the contact 2t from the contact 60 by a rotating action, section C of Figure illustrating the peeling action being completed and section U showing the contacts disengaged thereafter.

I have found that a construction oi" this character will separate contacts which are stuck so badly that they cannot be separated by other means such as a straight line rather than a lo tating separation or a sliding motion of one con tact on the other and thus sticking of the coin tacts is entirely eliminated.

The particular bimetal element 54 disclosed and formed in a zigzag shape makes it possible to use a bimetal element of considerable length to obtain proportionally greater travel of the controlling end of the armature in less space than with the ordinary spirally arranged bimetal element.

Also less pendulum effect is experienced with this type of bimetal element than with the spiral type. A further advantage is that the element, in responding to temperature changes, so warps that the armature 5B swings about the approximate center of the area of the bimetal element instead of producing a combination swinging and sliding eifect as experienced with spirally wound bimetal elements when the pull of the magnet 18 tends to prevent the contacts from separating.

The heater 16 tends to decrease the differential of operation of the switch and thus compensate for an increase in its differential of operation caused by using the magnet l8. To accomplish this desired compensation, the heater 16 can be designed to radiate more heat than would be required if the magnet i8 were not provided and the heater were used in connection I with a thermostat devoid of any influence corresponding to the magnet 18.

Some changes may be made in the construction and arrangement of the parts of my device without departing from the real spirit and purpose of my invention, and it is my intention to cover by my claims, any modified forms of structure or use of mechanical equivalents, which may be reasonably included within their scope.

I claim as my invention:

1. In a switch structure, a magnet, an arma ture movable relative thereto, a contact carried by said armature, a contact for coaction therewith, a carrier element for said second contact and a leaf spring, said second contact being mounted thereon, said leaf spring being arranged to cause said second contact to normally engage said carrierelement, said second contact being movable from engagement therewith only under constraint of said leaf spring.

2. In a switch'structure, a magnet, an armature movable relative thereto, a contact carried by said armature, a contact for coaction therewith, a carrier element for said second contact and a spring, said second contact being mounted thereon, said spring being arranged to cause said second contact tonormally engage said carrier element, said second contact being movable from engagement therewith only under constraint of said spring.

3. In a switch structure, a magnet, an armature movable relative thereto, a contact carried by said armature, a contact 'for coaction therewith, a carrier element for said second contact and a leaf spring, said second contact being mounted thereon, said leaf spring being arranged to cause said second contact to normally engage said carrier element, said second contact being movable fromengagemcnt therewith only under constraint of said leaf spring, said carrier element being adjustable to stop said armature closer or farther from said magnet.

said spring, said carrier element being adjustable to stop said armature closer or farther from said magnet.

5. In a switch structure, a magnet, an armature movable relative thereto, a contact carried by said armatureja contact for coaction therewith, a carrier element for saidsecond contact, a leaf spring, said second contact being mounted thereon, said leaf spring being arranged to cause said second contact to normally engage said carrier element, said second contact being movable from engagement therewith only under constraint of said leaf spring and means for actuating said armature comprising a bimetal element anchored at one end and operatively connected with said armature at its other end and doubled in zigzag formation between its ends.

6. In a switch structure, a magnet, an armature movable relative thereto, a contact carried by said armature, a contact for coaction therewith, a carrier element for said second contact, a spring, said second contact being mounted thereon, said spring being arranged to cause said second contact to normally engage said carrier element, said second contact being movable from engagement therewith only under constraint of said spring and means for actuating said armature comprising a bimetal element anchored at one end and operatively connected with said armature at its other end and doubled in zigzag formation between its ends.

7. In a switch structure, a magnet, an armature movable relative thereto, a contact carried by said armature, a. contact for coaction there,-

with, a carrier element for said second contact, a leaf spring, said second contact being mounted thereon, said leaf spring being arranged to cause said second contact to normally engage said carrier element, said second contact being movable lfrom engagement therewith only under constraint of said leaf spring and means for actuating said armature comprising a bimetal element anchored at one end and operatively connected with said armature at its other end and doubled in zigzag formation between its ends, said carrier element being adjustable to stop said armature closer or farther from said magnet.

8. In a switch structure, a magnet, an armature movable relative thereto, a contact carried by said armature, a contact for coaction therewith, a carrier element for said second contact, a spring, said second contact being mounted thereon, said spring being arranged to cause said second contact to normally engage said carrier element, said second contact being movable from engagement therewith only under constraint of said spring and means for actuating saidw armature comprising a bimetal element anchored at one end and operatively connected with said armature at its other end and doubled in zigzag formation between its ends, said carrier element being adjustable to stop said armature closer or farther from said magnet.

9. ma switch structure, a magnet, an armature movable relative thereto, a contact carried by said armature, a contact for coaction therewith, a carrier element for said second contact, a spring, said second contact being mounted thereon, said spring being arranged to cause said second contact to normally engage said carrier element, said second contact being movable from engagement therewith only under constraint of said spring and means for actuating said armature comprising a bimetal element anchored at one end and operatively connected with said armature at its other end and doubled in zigzag formation between its ends, said bimetal element at its anchored end having a leaf spring secured thereto and the leaf spring being anchored.

10. In a switch structure,'a magnet, an armature movable relative thereto, a contact carried by said armature, a contact for coaction therewith, a carrier element for said second contact, a spring, said second contact being mounted thereon, said spring being arranged to cause said second contact to normally engage said carrier element, said second contact being movable from engagement therewith only under constraint of said spring, means for actuating said armature comprising a bimetal element anchored at one end and operatively connected with said armature at its other end and doubled in zigzag formation between its ends, said bimetal element at its anchored end having a leaf spring secured thereto and the leaf spring being anchored and means for adjusting the range of said bimetal element comprising an adjusting screw engageable with said leaf spring.

11. In a switch structure, a switch arm, a contact carried thereby, a second contact for coaction with the contact on said switch arm, a carrier element for said second contact, a leaf spring, said second contact being mounted thereon, said leaf spring being arranged to cause said second contact to normally engage said carrier element, said second contact being movable from engagement therewith only under constraint of said leaf spring and means for actuating said switch arm comprising a bimetal element anchored at one end and operatively connected with said arm at its other end and doubled in zigzag formation between its ends.

12. In a switch structure, a switch arm, a contact carried thereby, a second contact for coaction with the contact on said switch arm, a carrier element for said second contact, a spring, said second contact'being mounted thereon, said spring being arranged to cause said second contact to normally engage said carrier element, said second contact being movable from engagement therewith only under constraint of said spring and means for actuating said switch arm comprising a bimetal element anchored at one end and operatively connected with said arm at its other end and doubled in zigzag formation between its ends.

'13. In a switch structure, a magnet, an arma ture movable relative thereto, a contact carried by said armature, a contact for coaction therewith, a carrier element for said second contact, a leaf spring,.said second contact being mounted thereon, said leaf spring being arranged to cause said second contact to normally engage said carrier element, said second contact being movable from engagement therewith only under constraint of said leaf spring and means for adjusting the differential of operation of said switch structure comprising an adjusting element for moving said carrier element and said leaf spring whereby said armature in closed contact posi tion may be in a stronger or weaker magnetic field as desired.

14. In a room thermostat, a temperature responsive switch including a temperature respom sive element, said switch having an inherent differential of operation, magnetic means to provide snap action Ior saidvswitch and which in creases said differential of operation and heating means adjacent said temperature responsive element and operable upon closure of said switch to modify the action thereof to cause said switch to open sooner than it otherwise would without said heating means and thus decrease the diiferential of operation and compensate for the increase thereof caused by said magnetic means.

15. In a room thermostat, a temperature responsive switch including a temperature responaowaoc sive element, said switch having an inherent thi Ierential of operation, magnetic means to pmvide snap action for said switch and which its creases said differential of operation, heating means adjacent said temperature responsive element and operable upon closure of said switch to modify the action thereof to cause said switch to open sooner than it otherwise would without said heating means and thus decrease the diner entiai of operation and compensate for the in crease thereof caused by said magnetic means and means for changing the differential of opera tion of said switch by varying the relative position of the switch and the magnetic means when the switch is in closed circuit position.

16. In a switch structure, a switch arm, a contact carried thereby, a second contact for coac tion with the contact on said switch arm, and means for actuating said switch arm comprising a bimetal element anchored at one end and operatively connected with said arm at its other end and doubled in zigzag formation between its ends.

LAWRENCE M. PERSONS. 

